Substantial attention has been directed in recent years toward composite materials capable of exhibiting negative effective permeability and/or negative effective permittivity with respect to incident electromagnetic radiation. Such materials, often termed metamaterials, usually comprise periodic arrays of electromagnetically reactive cells that are of substantially small dimension (e.g., 20% or less) compared to the wavelength of the incident radiation. A metamaterial can comprise a dielectric patterned with one or more conductors (for example, a dielectric substrate patterned with metallic split-ring resonators), or alternatively can comprise conductors patterned with one or more dielectrics (for example, a so-called “fishnet” structure in which a conductive sheet is patterned with air holes). Although the individual response of any particular electromagnetically reactive cell to an incident wavefront can be quite complicated, the aggregate response across the population of electromagnetically reactive cells can be described macroscopically, as if the composite material were a continuous material, except that the permeability term is replaced by an effective permeability and the permittivity term is replaced by an effective permittivity. Depending on the size, structure, and arrangement of the electromagnetically reactive cells, as well as the frequency at which incident radiation is applied, certain metamaterials can sometimes simultaneously exhibit both a negative effective permeability and a negative effective permittivity, such metamaterials being termed negative index materials.
Potential industrial applicabilities for metamaterials and negative index materials include so-called superlenses having the ability to image far below the diffraction limit to λ/6 and beyond, new designs for airborne radar, high resolution nuclear magnetic resonance (NMR) systems for medical imaging, microwave lenses, and other radiation processing devices. Issues arise in the realization of useful devices from such composite materials. By way of example, incident radiation can experience substantial power loss while propagating through many known metamaterials and negative index materials. Other issues arise as would be apparent to one skilled in the art in view of the present disclosure.